Bacterial Lymphadenitis

Bacterial lymphadenitis is infection of one or more lymph nodes by bacteria, regional (draining a local site) or generalised (bacteraemia). Causes include Staphylococcus aureus, group A streptococcus, anaerobes, Bartonella henselae, Yersinia pestis (bubonic plague), Francisella tularensis, Brucella, Treponema pallidum, Haemophilus ducreyi, Chlamydia trachomatis (LGV) and mycobacteria.

• Site of the nodes points to the source: cervical (throat, teeth, scalp), axillary (arm, breast), inguinal (leg, genitals, perineum).

Tender, enlarged, warm node with fever and malaise; node may suppurate.

• Specific patterns: bubonic plague (very painful bubo, high fever, prostration, rodent or flea exposure, endemic foci in Kenya); cat scratch disease (papule then node 1 to 3 weeks); LGV (inguinal buboes with groove sign); chancroid (painful ulcer and suppurative nodes); syphilis (rubbery painless nodes); brucellosis (generalised, fever, sweats).
• Differential diagnosis: viral lymphadenitis, tuberculosis, lymphoma, leukaemia, HIV, sarcoidosis, drug reaction, metastatic cancer, Kawasaki disease, toxoplasmosis.
• Complications: abscess, sepsis, bacteraemia, sinus formation, chronic lymphoedema, septic shock (plague), dissemination.

Directed by site and exposure history.

• Full blood count, CRP, blood cultures; aspirate or biopsy for Gram stain, culture, PCR; Bartonella, Brucella, syphilis and HIV serology; STI swabs; Xpert MTB/RIF.
• Ultrasound; chest radiograph; plague: bubo aspirate PCR and rapid antigen test with immediate notification.

Targeted antibiotics with drainage by needle aspiration.

• Supportive: analgesia, fluids, rest, warm compress, treat primary lesions, contact tracing and notification where relevant.
• Pharmacological: non specific pyogenic: flucloxacillin 500 mg to 1 g four times daily for 7 to 10 days (clindamycin 300 to 450 mg three times daily if allergic). Cat scratch disease: azithromycin 500 mg then 250 mg daily for 4 days. Bubonic plague: gentamicin 5 mg/kg IV daily, or doxycycline 100 mg twice daily, for 10 days (ciprofloxacin 500 mg twice daily alternative). Tularaemia: gentamicin 5 mg/kg IV daily for 10 days. Brucellosis: doxycycline 100 mg twice daily with rifampicin 600 to 900 mg daily for 6 weeks. LGV: doxycycline 100 mg twice daily for 21 days (azithromycin 1 g weekly for 3 weeks in pregnancy). Chancroid: azithromycin 1 g single dose or ceftriaxone 250 mg IM single dose. Syphilis: benzathine benzylpenicillin 2.4 million units IM.
• Procedures: needle aspiration of buboes and fluctuant nodes through healthy skin (avoid incision in LGV and plague); incision and drainage for staphylococcal abscess.
• Special groups: pregnancy, azithromycin or amoxicillin as appropriate and avoid doxycycline, and monitor gentamicin levels; children, weight based doses; HIV, broaden the search for tuberculosis and fungal infection.
• Red flags: fever with prostration and painful bubo, rapid enlargement, sepsis, nodes with fixed hard consistency, weight loss.
• Follow-up: review at 48 to 72 hours; partner notification for STIs; notify public health authorities for plague.